Period diary: your dates, kept on your own device

How it works

• A period asks for the first day, the last day if it has ended, how heavy it got, and anything that came with it.
• Past periods count too. Put in the ones you remember or have on a calendar. Two first days are enough for the page to count one gap.
• My periods lists them, newest first, with how long each lasted and how many days after the one before it started. It ended today adds the last day in one tap.
• Looking back shows which day you are on today, and the shortest, longest and average gap of your last six.
• Print my sheet makes a table of your periods with empty rows to fill in by hand.

What this page can’t do

• It is not birth control. It cannot tell you which days you can or cannot get pregnant, and nobody should rely on it for that.
• It cannot tell whether you are pregnant. A late period has many causes. A pregnancy test or a clinic can tell; this page cannot.
• It does not forecast. It adds your past gaps to your last first day and shows the dates that gives. Bodies do not keep to averages.
• It does not diagnose anything and is not treatment. It cannot tell why a period is late, heavy, painful or missing.
• It cannot remind you. It has no alarm and sends no message.
• The diary does not move to another phone or computer by itself. Print it, download it, or use My data on this device to carry a backup across.

When to show it to someone

The U.S. Office on Women’s Health, a federal office, says to talk to a doctor or nurse when:

• your cycles, counted from one first day to the next, are shorter than 24 days or longer than 38 days;
• you have no period for 90 days and you are not pregnant or breastfeeding;
• a period lasts longer than eight days;
• you bleed through one or more pads or tampons every one to two hours, or pass clots larger than a quarter;
• you feel dizzy, lightheaded, weak or tired, or have chest pain or trouble breathing during or after your period;
• pain medicine from the store does not help, or the pain keeps you from work or school.

It also says that for a few years after a first period, cycles longer than 38 days are common. We read these on its pages Your menstrual cycle and Period problems on October 5, 2026. They are that office’s words, shortened; we added nothing of our own. If you are worried and none of these fits, that is still a good enough reason to ask.

Where the idea comes from

Keeping track of periods on a calendar or in a diary is ordinary advice: the Office on Women’s Health says a record of your periods and symptoms can help a doctor or nurse work out what is going on. Many phone apps do this and keep the dates on a company’s computers. This page does the counting and keeps nothing anywhere but here. It is not any clinic’s official form, and no doctor or nurse has looked at it.